This invention relates to a sharpening machine for root-cutter knives, which comprises a jaw device for supporting a knife to be sharpened, said knife having a serrated edge to be sharpened, a magazine for knives to be sharpened, a device for feeding singly a knife from the magazine to the jaw device, a rough-sharpening device and a finesharpening device for the knives, said sharpening devices each comprising a milling device having a rotary milling cutter, the jaw device being rotatably mounted on a shaft in parallel relationship with the milling cutter rotating shaft, and means being provided to periodically swing the jaw device about the shaft thereof between a position where the knife engages the milling cutter and a rest position where the knife does not engage the milling cutter, the machine comprising moreover a rack-and-rachet mechanism for stepwise movement of the milling cutter relative to the jaw device as well as a cam shaft for controlling the swinging of the jaw device and the rack device.
The root-cutter knives, also known as Koenigsfeld's knives, are comprised of a plate terminating in a corrugated or serrated cutting edge.
The sharpening of such knives comprises the following operations:
1. a dressing or milling of the cutting face which removes the remaining portion of the cutting edge obtained during the previous sharpening; PA1 2. a first rough sharpening or breaking-down which cuts into the one knife serrated surface over a few millimeters to have said surface form a very acute angle with the other surface; PA1 3. a second fine sharpening which cuts into the knife over about one millimeter to sharpen the knife; PA1 4. a deburring which removes the small chips which remain attached to the knife.
Until recent times, said four operations have been performed on a separate machine; each machine had to be fed separately, the required manpower for the sharpening thus being rather large.
A machine has been proposed to perform the breaking-down and fine-sharpening operations on the knives. In said known machine, the worn knives, previously milled, are stored inside a magazine from which they are fed one by one to a first jaw device which is so arranged that the knive is moved stepwise in front of a breaking-down device; thereafter, the knife is released from the first jaw device and it is taken over by a second jaw device which moves again stepwise the knife in front of the milling cutter in the finesharpening device. Finally the knife is released and falls into a store for machined knives.
This invention has for object to provide a sharpening machine for root-cutter knives, which allows to perform the four operations required for the sharpening, which is compact, simple as regards the parts and movements, and in which each knife to be sharpened is arranged from start to finish of the operations, in one and the same jaw device.
For this purpose, the machine according to the invention comprises a horizontal conveyor on which are mounted a plurality of jaw devices, said conveyor having a plurality of stopping positions in each one of which a jaw device is arranged in front of the magazine and in front of each one of the sharpening devices, each sharpening device comprising a milling device which is slidingly mounted on the rotating shaft thereof and a lever block to which is associated the rack-and-rachet mechanism which is connected to the milling device and which comprises a member for pushing the jaw device to swing same from the non-engagement position thereof to the engagement position where the knife engages the milling cutter, and each jaw device comprising a fixed jaw rotatingly mounted about said swinging shaft and having a knife supporting plate, and a movable jaw frame integral with the fixed jaw and comprising a plunger for pushing the knife against the plate, slidingly arranged in the movable jaw frame, directed upwards and bearing at the top thereof a jack for operating said plunger, a return member being associated to said movable jaw frame to swing said device towards the rest position thereof, the knife-supporting plate bearing an ejector slide arranged in the path of said knife and a spring member for moving the slide along a direction which corresponds to the ejection of the knife from the jaw, the magazine comprising a knife-stacking area and a knife-pushing slide arranged at the stack bottom on the fixed jaw plate and operating against the ejector slide spring, and said horizontal conveyor bearing members for operating the jaw device jacks, so as to bring the jack in each jaw device to a position in which said jack causes the plunger to move away from the plate before said device being located in front of the magazine.